This invention relates to sawmills, and particularly to sawmills adapted to recover lumber products from short logs.
Standard sawmills are often unable to recover good quality lumber from short logs, i.e. 8 feet and under, resulting in waste of potential lumber material as wood chips. While some innovative sawmills have attempted to address this need, the present invention provides a novel means of recovering a maximal amount of high-quality lumber from logs under 8 feet.
The development of the present invention was necessitated by the limitations of the standard sawmills in the industry in addressing short log lumber recovery. In particular, some means are required for recovering lumber products with a minimal amount of waste chip production.
In response to this problem, the present invention seeks to provide an apparatus and process for maximizing high-quality lumber recovery while limiting the amount of waste wood chips. In order to accomplish this, the present invention comprises a novel positioning and cutting apparatus which, when employed in the manner set out below, will allow lumber processing companies to maximize yield from short logs of previously little recoverable value. A log is positioned in a log cradle, stabilized by means of end dogs, and passed through band saw cutting means by means of overhead log carriages, but the log can be returned to its initial pre-cutting location any number of times and rotated through a full 360 degrees by a log-turning device to any desired position before again passing the log through the cutting means. Scanning means are employed to determine log diameter to enable cradle adjustment and initial log positioning.
While the standard sawmills usually cannot economically recover lumber from logs less than 8 feet in length, the present invention can quickly and efficiently process such logs into boards ranging from 2 inchesxc3x97xc2xd inchxc3x971 foot to 10 inchesxc3x9710 inchesxc3x978 feet. In addition, the present invention is compact in size and can be used either in concert with existing sawmills or as a stand-alone unit for small-log operations. Also, the fully rotatable positioning mechanism allows for tangential cuts at any face rather than the usual four faces possible in standard sawmills, enabling maximal yield. Another feature of this invention is the use of band saws rather than the standard circular saws, which allows for cutting of logs up to 28 inches in diameter.
Prior attempts to provide small log recovery sawmills include U.S. Pat. No. 4,117,755, wherein is disclosed a log sawing and transport system that positions a log, uses end dogs to secure it, and moves the log through cutting means with axially moveable carriage units. However, this apparatus fails to maximize high-quality lumber recovery, as it employs circular saws to produce sector-shaped pieces. At least one of the saws can be adjusted to different angles, but this is addressed to the specific problem of quarter-sawing rather than recovery of high-quality boards.
Other prior art has addressed related problems. U.S. Pat. No. 3,459,246 discloses a lumber plant that employs band saws adjustable to the diameter of a given log, using scanning means to determine the diameter. Also, logs are gripped at their ends to be transported through paired cutting means. However, this invention fails to consider problems of yield maximization of short logs, as it primarily addresses band saw adjustment.
Canadian Patent No. 1,108,968 discloses a scrag saw mill dogging system that employs dogs on moveable carriages. However, the dogs attach to the log""s sides, the carriages are not utilized during the actual cutting phase, and the invention is directed specifically to a problem associated with scrag saw mill operation.
Multiple passes through cutting means (e.g. U.S. Pat. No. 5,503,202) and rotatable dogging means (e.g. U.S. Pat. No. 5,421,385) are known in the art, but they are not directed towards short log lumber recovery maximization as in the present invention.
The present invention offers a novel solution to the problem of efficient and cost-effective small log lumber recovery. The innovative use of an adjustable log cradle, rotating end dogs, movable carriages, adjustable band saws, and other features addresses a serious lumber industry waste issue.
The principal object of this invention is, therefore, to seek to provide a lumber-processing apparatus and method adapted to the specific problem of short log recovery, the apparatus comprising means for rotating, transporting, and cutting short logs. The method uses the disclosed apparatus to make particular cuts of a short log.
Other objects will appear from the description and the drawings.
Accordingly, the present invention provides an end-dogging head saw comprising a log cradle for supporting a log, a log-turning device for rotating the log into proper alignment with a pair of band saws, the log-turning device depending from overhead log carriages which move the log into contact with the band saws, and a carriage drive for powering the overhead log carriages, whereby short logs can be quickly and efficiently processed. The invention also seeks to provide a method for using the apparatus, comprising rotation of a log through 360 degrees to allow for cutting at any desired angle along the length of the log. The method allows for maximal recovery of high-quality lumber.